Control mechanism



Filed Sept. 25, 1937 '2 Sheets-Sheet 2 FIG. 2.

FIG. 3;

l i III WITNESSES:

INVENTOR ROGERW-HHSTING6 I AT'FOR Y Patented Dec. 24, 1940 UNITED STATES PATENT OFFICE CONTROL MECHANISM Pennsylvania Application September 25, 1937, Serial No. 165,637

14 Claims.

inexpensive to construct and which is compact so that it occupies a small amount of space.

A further object of the invention is to provide improved means for adjusting a control mechm anism employing an overcenter spring strip for imparting snap action to the switch thereof.

A still further object of the invention is to provide an improved readily accessible adjusting mechanism for a refrigerator control that is movable to a plurality of selective positions for adjusting the temperatures to which the control responds, and having means for adjusting said temperatures relative to the various positions of the adjusting mechanism.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a sectional view, somewhat diagrammatic, of a conventional domestic refrigerator having my improved control mechanism applied thereto;

Figs. 2 and 3 are longitudinal sectional views taken in planes at right angles to each other through the control mechanism shown in Fig. 1; and,

Fig. 4 is a transverse sectional view taken along the line IV-IV of Fig. 3.

The control mechanism disclosed in the present application defines an improvement over the mechanism shown and claimed in the copending application of Richard H. Proctor, Serial No.

124,251, filed February 5, 1937 and assigned to the assignee' of the present application. Both of these control mechanisms employ a springstrip for imparting snap-action to the control switch during .its opening and closing movements, the structure claimed in the present application representing an improved organization of the elements of the mechanism shown in the copending application with additional features not disclosed therein.

Reference will now be had to Fig. 1 wherein I have chosen to show my improved mechanism applied to a conventional domestic refrigerator having a cabinet structure II), the upper portion of which is formed of a plurality of insulated walls H for defining a cooling chamber l2. A machinery compartment I3 is formed at the-bottom of the cabinet. for housing a refrigerant condensing unit generally shown at H and including a compressor IS, a motor l6 for driving the same and a condenser II. The latter is cooled in any well known manner such as, for example, by a fan l8, that circulates cool air from the room atmosphere in heat transfer relation with the compressor l and condenser ll in a well understood manner.

Cooling of the air in the cooling chamber I2 is effected by suitable evaporator structure I9 having'a wall 2| covering the front side thereof and including a door 22 for providing access to freezing trays (not shown) in the interior of the evaporator structure. include a header 23 from which vaporized refrigerant is withdrawn by the compressor I5 through a conduit 24. Condensed refrigerant is conveyed to the evaporator ill from the condenser H by means of a conduit 25 having a suitable expansion device connected thereto and diagrammatically shown at 28.

It will be apparent to those skilled in the art that the apparatus described heretofore operates on the well known compressor-condenser-expander cycle so that no further description of the construction or operation is deemed necessary. Operation of the condensing unit I4 is controlled by an improved thermostatic switch structure generally indicated at 21, and constructed in accordance with my invention. While I have shown my improved control applied to a domestic re frigerator of the compression type, it will be understood that it is not so limited but is applicable to various types of refrigerating apparatus employing other forms of refrigerating machines.

Reference will now be had to all figures of the drawings for a detailed description of the construction of the control device 21 which includes a casing 28 for housing a bellows 29, a yoke member 38 actuated thereby, a main spring 32 for biasing the yoke 3| in opposition to the bellows 29 and a switch structure 33 that is opened and closed by the movement of the bellows as described hereinafter. Energization of the compressor motor I6 is controlled by the switch structure 33, the latter being connected in a conductor 34 forming a part of the motor circuit 35, that is connected to a suitable source of power (not shown).

The bellows 29 is secured to the casing 28 in any suitable manner, such as, for example, by a locking nut 36. A tube 31 communicates with the interior of the bellows 29 and has an end 38 The evaporator l9 maythereof closed and disposed within the cooling compartment l2 and preferably secured to the evaporator structure IS. The tube 31 and bellows 29 define a space for a volatile fluid, the pressure of which is a function of the temperature of the tube and 38 and evaporator structure l9, as is well understood. The free end of the bellows 29 is secured to the yoke member 3| by means of a clamp 4|, soldered or otherwise fixed to the bellows and having its edge portion bent over a flange 42 formed on the yoke member 3|.

Laterally extending arms 43 are provided on the yoke member 31 and are movable between stops 44 and 45 carried by a U-shaped bracket 46 that may be clamped between the fixed end of the bellows 29 and the housing 28. The stops 44 and 45 provide limits for the movement of the bellows 29. Normally, the movement of the bellows 29 is within the limits determined by the stops. The yoke member 3| is notched as shown at 41 for the reception of a bowed spring strip 48 preferably crimped at 49. The spring strip 48 defines an element of a snap-acting mechanism to be referred to more in detail hereinafter.

The bias of the main spring 32 may be adjusted by an adjusting mechanism, generally indicated at and including a hollow shaft 52 rotatably carried by the casing 28 and having a small portion thereof splined internally at 53. A stud 54 is disposed within the shaft 52 and includes a splined collar 55 that fits within the splined portion 53 of the shaft 52 and a. portion 58 threaded in a thrust washer 51. The latter is engaged by the spring 32 and is movable axially of the stud 56 as the latter is rotated whereby the bias of the spring 32 is varied. Rotation of the washer 51 is prevented by a fin 58 secured to the casing 28 and disposed within a slot 59 in the washer 51.

The shaft 52 projects through an opening 6| in the front wall 2| of the evaporator and is provided with a handle or knob 62 readily accessible to the operator. The wall 2| may be provided with indicia as shown in Figs. 1 and 4 that is readable in conjunction with a pointer 63 on the knob 62 for indicating the position to which the control is adjusted. It is desirable that the bias of the main spring 32 may be adjusted relative to the shaft 52. and knob 62 in order that the proper temperatures at which the switch is opened and closed in the various positions of the control may be obtained. Accordingly, the stud 54 is provided with a slot 64 for the reception of a screw driver or similar tool. When an adjustment is to be made, sufficient pressure is applied to the screw driver to compress the spring 32 and force the splined shoulder 55 out of engagement with the internal spline 53. A turn of the stud 54 one way or the other is made and the spring 34 is permitted to force the stud back to its normal position and to engage the splined portions of the stud and shaft. Accordingly, the bias of the spring 32 is adjusted relative to the shaft 5 The switch structure 33 includes a pair of stationary contacts 66 that are carried by an insulating terminal board 61, the latter being secured to the casing 28 in any suitable manner. Preferably, the board 61 is provided with a pair of holes 18 which pass over respective tongues 12 formed on the casing 28, the tongues 12 being bent as shown in Fig. 3 after assembly of the board 61 to the casing 28. Terminals 68 are provided for the respective contacts 66 and are connected to portions of the conductor 34. A

gasketed cover 69 is provided for the terminals and secured by a screw 1| to the casing 28.

A movable contact 13 cooperates with the contacts 66 and is carried by an insulating support 14 forming a part of a lever structure 15; the latter being pivoted at 16 in an intermediate portion of the casing 28. Preferably, the lever 15 is pivoted in a bracket 11 that is supported by the terminal board 61. Accordingly, the switch structure 33 and the lever structure 15 may be assembled to the board 61 and these assembled elements may then be attached to the casing 28 as a unit.

As best shown in Fig. 3, the lever'structure 15 includes a laterally extending portion composed of spaced arms 18 and 19 which are disposed on opposite sides of the spring strip 48 and which are alternately engaged by the strip 48 as it snaps from one position to another. An adjustable stop 8| is provided for determining the switch open pOsition of the lever structure 15 and an adjustable spring 82 biases the lever in its switch closed position. The bias of the spring 82 is, of course, less than the bias of the spring strip 48 except at the moment when the latter snaps to its switch closed position. Adjustment of the bias of the spring 82 varies the temperature at which the spring strip 48 closes the switch 33 and therefore the temperature differential or the difference in temperatures at which the switch 33 is opened and closed is varied. Further reference to the operation of the spring 82 is made hereinafter.

Means is provided for maintaining the switch 33 open in one position of the adjustable means 5| and closed in a second position thereof regardless of the temperature of the evaporator l8 and the control tube 31. A cam 83 is secured to the hollow shaft 52 for rotation therewith and includes a projecting portion 84 having seats 85 and 86 formed therein. Surfaces 81 and 88 of the cam portion 84 are inclined with respect to the radius for a purpose to be referred to hereinafter. The cam 83 is also provided with a projection 89 engageable with a stop 9| suitably formed on the interior of the casing 28 as shown in Figs. 3 and 4. The projection 89 engages one side or the other of the stop 9| in the terminal positions of the adjusting mechanism 5|. The projecting portion 84 of the cam 83 is disposed in a plane offset from the plane of the stop 9| in order that it will clear the stop as the cam is rotated. (See Fig. 3.)

A pin 92 is provided on the end of the lever structure 15 that is engageable with the pro-- jecting portion 84 of the cam 83 and is seated in the seat 86 when the control is in the off position and in the seat 85 when the control is in the run position. (See Fig. 4.) Accordingly, the switch 83 is held open and closed by the cam 83 when the adjusting means 5| is in its respective oil? and run positions regardless of the temperature of the evaporator I9.

Operation As shown, the control mechanism is adjusted to operate at a relatively high temperature; the

control indicator 63 being adjusted to a position is moved by the expanding bellows 29 and carries the ends of the spring strip 48 with it. Movement of the center of the strip 48 is prevented as the lever I and arm 18 are held by the stop 8|. At a predetermined point in the movement of the yoke 3| corresponding to the high temperature limit of 42 F., the center of the spring strip 48 passes through dead center and its stressed condition causes the strip 48 to snap overcenter. This movement eifects engagement of the strip 48 and the arm 19 and counter-clockwise movement of the lever 15 so that the switch 33 is closed and operation of the compressor I 5 is initiated.

Evaporation of refrigerant is efiected in the evaporator for cooling the chamber l2. -Accordingly, as the temperature of the evaporator I9 is depressed, the bellows 29 is contracted by the spring 32 and carries the yoke 3| and the ends of the spring strip 48 with it. Movement of the center of the strip 48 is prevented by the arm 19. When the spring strip 48 reaches dead centencorresponding to a temperature of 30 F. the stressed condition thereof causes the center to snap to the position shown in the drawings. Accordingly, the lever is moved clockwise in opposition to the bias of the spring 82, and the switch 33 is opened for terminating operation of the compressor IS.

The temperature differential at which the control operates may be varied by adjusting the bias of the spring 82. Increasing the bias of the spring 82 increases the pressure on the center of the spring strip during the open period of the switch, and, therefore, the strip 48 will snap overcenter at reduced'amplitudes of the bellows 29 corresponding to reduced evaporator temper-atures. Adjustment of the bias of the spring 82 varies the closing temperature of the switch 33 without afiecting the opening temperature thereof and, therefore, the temperature diflercntial at which the control operates is varied. The opening temperature is not affected by adjustment of the bias of the spring strip 48 except at the time that the latter snaps to its switch closed position. Rotation of the knob 62 counter-clockwise as viewed in Fig. 4 reduces the bias of the main spring 32 and, therefore, lower pressures in the bellows 29, corresponding to lower evaporator temperatures will effect opening and closing of the switch 33. The position marked I is the coldest position wherein cycling of the compressor is effected. Movement of the control knob 82 to the run position eifects continuous operation of the compressor I5 for quickfreezing operations. As the cam portion 84 approaches the pin 92 during a movement of the knob 62 to the run position, the inclined surface 8'! engages the pin 92 and moves it to the left as viewed in Figs. 3 and 4 whereby the lever 15 is rotated to its switch closed position, in opposition to the bias of the spring strip 48. The pin 92 is locked in the seat 85 in this position of the control knob 62.

Rotation of the knob 82 to the off position efi'ects engagement of the inclined surface 88 with the pin 92 if the lever 25 is in the switch closed position so that the pin 92 is moved to the right as viewed in Figs. 3 and 4. Accordingly, the lever 15 is moved to its switch open position against the bias of the spring strip 48. In the "run position of the control the pin 92 is locked in the seat 88 and the switch 33 is maintained open regardless of the temperature of the evaporator l9.

From the foregoing, it will be apparent that I have provided an improved, inexpensive and compact control mechanism for temperature changing apparatus which may be readily adjusted to a plurality of selective positions for the maintenance of difierenttemperatures. The mechanism includes improved means for maintaining the switch closed and open in the respective terminal positions of the adjusting means and furthermore provides for the adjustment of the tem perature differential to be maintained.

I have shown my improved control mechanism While I have described my improved mechanism as temperature responsive, it will be understood that it may be utilized as a pressure responsive control.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is: V

1. In apparatus for controlling the operation of a temperature changing machine, the combination of a bellows movable in response to the temperature produced by said machine, a switch structure for controlling the operation of the machine and actuated to its open and closed positions by the bellows, a spring biasing the bellows for determining the temperatures at which said switch is opened and closed, means for adjusting the bias of said spring and movable to a plurality of selective positions and a single locking device movable with said adjusting means and effective in a pair of said selective positions for engaging said switch structure, whereby the switch structure is maintained in its open and closed positions, respectively, in said pair of selected posi-' tions.

2. In apparatus for controlling the operation of a temperature changing machine, the combination of a bellows movable in response to the temperature produced by said machine, a member actuated by said bellows, an adjustable spring for biasing the bellows, a bowed, overcenter spring strip carried by said member and movable at all times therewith, a switch structure for controlling the operation of the machine and actuated by said spring strip to its open and closed positions in a snap acting manner, means for adjusting the bias of said adjustable spring and means actuated by said adjusting means and eifective in one position thereof for locking said switch in one of its positions irrespective of movement of the spring strip.

3. The combination as claimed in claim 2 having adjustable means for biasing the switch toward one of its positions, whereby the temperature differential at which the switch is operated is varied.

4. In apparatus for controlling the operation of a temperature changing machine, the com- 5 bination of a bellows movable in response to the temperature produced by said machine, a yoke structure movable with said bellows, an adjustable spring engaging said yoke, a switch for controlling the operation of the machine, a bowed overcenter spring strip having its ends engaging said yoke structure for actuating the switch to its open and closed positions in a snap acting manner and means movable to a plurality of selective positions for adjusting the bias of said adjustable l5 spring and including means effective in a pair of said positions for locking said switch open and closed. i

5. In apparatus for controlling the operation of a temperature changing machine having a temperature changing element, the combination of a bellows movable in response to the temperature of said element, a yoke movable with said bellows, a bowed overcenter spring strip, the ends of which engage said yoke, a switch for controlling the operation of said machine and moved in a snap acting manner to its open and closed positions by said spring strip, a spring biasing said bellows for determining the temperatures of said element at which said switch is operated, means for adjusting the bias of the spring, and a locking member actuated by said adjusting means and effective in first and second positions of the adjusting means for locking the switch closed and open, respectively, regardless of the temperature of the element.

6. In apparatus for controlling the operation of a temperature changing machine having a temperature changing element, the combination of a bellows movable in response to the tempera- 40 ture of said element, a yoke movable with said bellows, a bowed overcenter spring strip, the ends of which engage said yoke, a switch for controlling the operation of said machine and moved in a snap acting manner to its open and closed positions by said spring strip, a spring biasing said bellows for determining the temperatures of said element at which said switch is operated, a spring nut for restraining said spring, means including a stud threaded in said nut and movable to a plu- 0 rality of selective positions for adjusting the bias of said spring, said stud being adjustable relative to said adjusting means for varying the relation between the bias of the spring and the position of the adjusting means, a locking member movable with said adjusting means and efiective in the terminal positions thereof for locking said switch closed and open, respectively, regardless of the temperature of said element and the position of the bellows.

7. In a control mechanism for a temperature changing machine, the combination of a fixed member, a switch for controlling the operation of the machine, means responsive to the temperature produced by the machine for actuating said switch and including a heat responsive element, a spring biasing said element for determining the temperature at which said switch is operated, a movable element for retaining said spring, a rotatable sleeve journaled in said fixed member, a

stud threaded in said movable element and normally lockedto said sleeve, and means for rotating the sleeve and stud, whereby the bias of the spring is adjusted, said stud being adaptable for axial movement and rotation in the sleeve and relative said fixed member, whereby the bias of the spring is adjusted independently of the sleeve.

8. In apparatus for controlling the operation of a temperature changing machine, the combination of a bellows movable in response to the temperature produced by the machine, a member 5 movable with the bellows, a spring for biasing the member in opposition to the bellows, said bellows member and spring being disposed substantially in alignment, means for varying the bias of the spring and adjustable to a plurality of se- 10 lective positions, a bowed overcenter spring strip having its ends engaging and movable with said member, a pivoted lever disposed adjacent to and beside the spring, an arm carried by said lever and coupled to a mid portion of the spring strip, a switch for controlling the operation of the machine and actuated by said lever, and means providing a connection between said pivoted lever and said adjustable means for maintaining the switch closed and open, respectively, in a pair of 20 positions of the adjustable means,

9. In apparatus for controlling the operation of a temperature changing machine, the combination of a bellows movable in response to the temperature produced by the machine, a mem- 25 ber movable with the bellows, a springfor biasing the member in opposition to the bellows, said bellows member and spring being disposed sub stantially in alignment, means for varying the bias of the spring and adjustable to a plurality of selective positions, a bowed overcenter spring strip having its ends engaging and movable with said member, a pivoted lever disposed adjacent to and beside the spring, an arm carried by said lever and coupled to a mid portion of the spring strip, an adjustable spring for biasing said lever toward one of its positions, a stop for determining the other position of the lever, a switch for controlling the operation of the machine and actuated by said lever, and means providing a connection between said pivoted lever and said adjustable means for maintaining the switch closed and open, respectively, in a pair of positions of the adjustable means.

10. In apparatus for controlling the operation of a temperature changing machine, the combination of a bellows movable in response to the temperature produced by the machine, a member movable with the bellows, a spring for biasing the member in opposition to the bellows, said 50 bellows member and spring being disposed substantially in alignment, a pair of stops for limiting the movement of the bellows, means for vary- Cal .ing the bias of the spring and adjustable to a plurality of selective positions, a bowed overcen- 55 ter spring strip having its ends engaging and movable with said member, a pivoted lever disposed adjacent to and beside the spring, an arm carried by said lever and coupled to a mid portion of the spring strip, an adjustable spring for bi- G0 ,asing said lever toward one of its positions, a

stop for determining the other position of the lever, a switch for controlling the operation of the machine and actuated by said lever, and means providing a connection between said pivoted le- 63 ver and said adjustable means for maintaining the switch closed and open, respectively, in a pair of positions of the adjustable means.

11. In a device for controlling the operation of temperature changing apparatus, the combination 7 0 of abellows movable in response to temperature,

a switch structure for controlling the operation of the temperature changing apparatus and actuated to its open and closed positions by the bellows, a spring biasing the bellows for determin- 75 ing the temperatures at which the switch is opened and closed, means for adjusting the bias of said spring and movable to a plurality of selective positions and a single locking device carried by said adjusting means and effective in a pair of said selective positions for locking said switch structure in its open and closed positions, respectively. 12. In a device for controlling the operation temperature changing apparatus, the combination of a bellows movable in response to temperature,

' a member actuated by the bellows, an adjustable spring for biasing the bellows, a. bowed, overcenter spring strip carried by said member and movable therewith at all times, a switch for controlling the operation .of the temperature changing apparatus and actuated by said spring strip to its open and closed position in a snap acting manner, means for adjusting the bias of said adjust- :able spring and means actuated by said adjustable means and effective in one position thereof for locking said switch in one of its positions irrespective of movement of the spring strip.

13. In apressure actuated switch, the combination of a bellows movable in response to pressure,

v-a yoke structure movable with said bellows, an ,adjustable spring engaging said bellows, a switch,

a bowed over-center spring strip having its ends engaging said yoke for actuating the switch to 30 its open and closed positions in a snap-acting manner, and means movable to a plurality of selected positions for adjusting the bias of said adjusting spring and including means effective in a pair of said positions for locking said switch open and closed.

14. In a mechanism for varying the bias of a spring controlling a temperature-responsive element; the combination of a retainer for engaging said spring; a shaft threaded in said retainer and adapted for rotation; a. collar on said shaft; a relatively fixed member; a sleeve around at least a portion of said shaft, journaled for rotative movement in said fixed member, and secured .to prevent axial movement in at least one direction relative thereto; a shoulder on said sleeve adapted to engage said collar to prevent axial movement of said shaft relative said sleeve in said one direction; said spring and retainer urging said shaft in said one direction; and an engagement between said sleeve and shaft for preventing rotative movement therebetween when the collar is adjacent said shoulder; said engagement and shoulder permitting axial movement of said shaft in said sleeve in a direction opposite saidone direction; whereby rotation of said sleeve effects movement of said retainer axially of said shaft when the collar is adjacent said shoulder but fails to effect such axial movement when the collar is not adiacent said shoulder.

ROGER. W. HASTINGS. 

